Journal of Photochemistry and Photobiology A: Chemistry 205 (2009) 197–202

LC.MS characterization of metoclopramide photolysis products

Aubert Maquille a,., Jean-Louis Habib Jiwanb
a Laboratory of Chemical and Physico-chemical Analysis of Drugs (CHAM), Louvain Drug Research Institute, Universite catholique de Louvain (UCL),
Avenue E. Mounier, 72 bte 7230, B-1200 Brussels, Belgium
b Laboratory of Mass Spectrometry, Universite Catholique de Louvain (UCL), 1348 Louvain-La-Neuve, Belgium

Abstract
The aim of this study was to investigate the photodegradation of the antiemetic drug metoclopramide.
Metoclopramide aqueous solutions were photoirradiated at 254 nm under argon atmosphere. Irradiated
metoclopramide solutions were analyzed by high performance liquid chromatography–ion trap mass
spectrometry in order to characterize photolysis products. Rapid decrease in metoclopramide purity, following
first-order kinetic, was observed following irradiation. The structures of 18 photolysis products
were tentatively identified based on their mass spectra and fragmentation. The main degradation mechanism
was scission of the chlorine which could be followed by polymerization of the resulting products
since dimeric and trimeric products were observed.